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Cross-sectional schematic of a SiGe fin heterostructure during Ge condensation. The piling up of Ge at the oxidation front to form a Ge-rich layer is shown. As oxidation proceeds, the Ge-rich layer increases in thickness and the fin width decreases. This also results in decreasing core thickness .
Cross-sectional TEM images of two SiGe fins after of Ge condensation. The oxidation temperature of is below the viscous flow temperature of thermal oxide of about , resulting in the unique geometry of the thermal oxide encapsulating the fin. The vertical sidewall surfaces of the SiGe fins also appear to be very smooth, making them suitable for FinFET applications where sidewall surface roughness would degrade carrier mobility dramatically at high electric field. The Ge atomic concentration values obtained by EDS at several locations in each fin are shown. (a) A wider fin showing the Ge-rich layer and the sandwiched core. (b) A narrower fin in which the Ge-rich layers have merged from opposite sides of the fin.
Ge concentration profile across a medium-width SiGe fin (, see inset) that has undergone of Ge condensation. The Ge concentration within the Ge-rich layer is quite uniform. The Ge concentration profile is observed to be rather abrupt at the interface between the Ge-rich layer and the substrate.
Cross-sectional TEM images highlighting dislocations in three SiGe fins of different fin widths after of Ge condensation. (a) A wide fin with a high dislocation density at the interface between the Ge-rich layer and the core. (b) A medium-width fin with a much lower dislocation density. (c) A narrow homogeneous Ge-rich fin (, Ge concentration) showing no observable dislocations.
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